In the processing of a wide variety of different products, and in particular in the processing of meat products as by cooking, smoking, chilling and the like, it is the practise to process the products in one or more processing chambers and to convey the products from one chamber, or through chambers divided into a series of different chamber zones. As the products dwell in the different chambers or zones, the atmosphere and the conditions within each chamber will be such as to produce a pre-determined processing action on the product, whether it be cooking, smoking, chilling, or any other process.
In order to produce a satisfactory end product and to produce uniformity and minimize wastage, it is necessary that the conditions throughout each chamber, or zone of the chamber system, shall be uniform from top to bottom and side to side. It is also necessary that the products dwelling within the chamber shall be supported or stored in such a manner that the atmosphere within the chamber can have full access to all of the products, both in the top and the bottom of the chamber and on both sides, to the fullest and extent.
In some processing systems, that the products are supported on a conveyor system which provides for continuous movement from zone to zone, so that the products are always moving through the zones during processing. However, such oven processing facilities occupy a substantial amount of floor area, and are somewhat costly to build.
In many cases therefore, it is desirable to process such products in batches. Such a batch of product would be typically be stored on a single storage device in the form of a rectangular cage-like device, open at the sides and the top and the bottom, and having shelves which are also of substantially open construction, so that the atmosphere within the zone can circulate throughout and around the products supported within the cage. However, the cage itself will remain essentially stationary during a pre-determined dwell time within a chamber zone or at a point in a chamber zone. Such systems have the advantage that they occupy less floor area and are more economical to build.
The processing conditions within any one zone of the chamber will of course be uniform, within that zone, or chamber. It will be appreciated that in some systems two or three or more separate chambers are provided, with the conveyor system running between them to carry the supported batches of product. In other systems, however, the chamber apparatus essentially is a continuous elongated rectangular chamber, and the interior is divided into separate chamber zones.
In the past, attempts have been made to provide such zone separations simply by air curtain type of barriers, but these have not been totally satisfactory. In fact, it is found greatly preferable to use actual doors between each of the zones, so as to as far as possible maintain a complete break between the condition of one zone and the condition of the next adjacent zone.
One of the problems in the design of an effective door system for separating the chambers or zones within a chamber, is that it is necessary to provide some activating means for opening and closing the doors. Usually, doors of this type are hinged along either side of the chamber, and swing from the centre of the chamber outwardly towards either side. It is found necessary to provide some form of means for opening the doors to permit a cage to pass therebetween, and to close the doors together again once the cage has passed. It might appear that all that is required is to provide a spring-loaded action on the door hinge of each of the doors, so that each door could simply swing open in response to movement of the cage, and swing closed once the cage had passed. However, industry standards for this type of equipment require that the cage shall be capable of passing through the doors without contact with the doors, and this standard therefore precludes this relatively simple solution.
In the past overhead conveyor rails have been provided, and at first sight such an overhead conveyor system does appear to offer advantages.
The conveyor system can readily be extended from either end of the chamber and continued to other areas of the processing facility for, for example, cutting, packaging and the like. However, in practise it has been found that there are certain disadvantages inherent in overhead conveyor systems for this type of processing facility. In particular, the interior of the chamber, and all accessories used within the chamber must be maintained totally clean and sterile. This may become difficult, particularly where an overhead conveyor system is used for carrying batches of product throughout other portions of the plant, where the conveyor system may become contaminated by grease, dirt and the like, which must then be cleaned off before the conveyor returns to the actual processing chamber. Lubrication of such overhead conveyors, if they have to pass through hot ovens, and through low temperature chilling rooms, also presents problems.
Clearly therefore it is advantageous to provide a conveyor system for use in such processing chamber facilities, which conveyor system is readily and easily accessible for a thorough cleansing operation, at regular intervals, so that dirt and contamination from other parts of the plant does not accumulate in the chamber.
It is particularly advantageous, if a conveyor system can be provided for conveying the cages through the processing chambers, which conveyor system terminates at or near to the entrance and exit points of the chamber, with other alternate conveyor means being provided running throughout the rest of the plant to and from those entrance and exit points. In this way any dirt or contaminate material on the conveyor running throughout the rest of the plant, will be isolated at the entrance and exit of the chamber, and the cage will be transferred from the one plant conveyor system to the other (chamber) system for passage through the chamber. Other advantages are obtained by such a system.
However, if the design of the chamber system, a continuous overhead conveyor rail is used, then the side walls of the chamber itself must incorporate structural members of sufficient strength to support the overhead conveyor system. This design requirement may interfere in some respects with the design of the chamber and its air circulating facilities, and cause unnecessary expense. In addition, in overhead conveyor systems, some small allowance must be made on either side for swinging movement of the cages. Thus when such overhead conveyor systems are used in a processing chamber, the side walls of the chamber must be spaced far enough apart that allowance is made for this small degree of movement, and this too may cause cost increases in the construction of the chamber and in its operation, which it would be desirable to avoid or at least reduce as far as possible.
Proposals have been made, in this type of processing chamber, utilizing cages for supporting products as they move into and out of the chamber, to simply support the cage on a system of wheels located on the underneath of the cage and running on the floor of the chamber.
This system has certain advantages, since it does not employ an overhead conveyor with all of its complications.
However, it is not always easy to maintain totally sterile sanitary conditions on the floor of the chamber. The wheels may pick up some contamination either outside the chamber or as they pass through the chamber, and this is unacceptable.